In a known ignition system for an internal combustion engine, the period of time in each ignition cycle during which the primary coil circuit is open can be maintained constant in the upper speed domain. Furthermore, the known system permits the ignition closure angle to be adaptable to the median speed domain by proper choice of the dimensions of the components. However, the known system has the disadvantage that the predetermined ignition timing characteristics lead to excessive primary circuit closure times in the region of engine idling, these times being greater than required for storing the necessary ignition energy so that energy losses result at low engine speed.